Adsorption of hydrophobic polyelectrolytes as studied by \emph{in situ} high energy X-Ray reflectivity

TL;DR

This study investigates how hydrophobic and hydrophilic polyelectrolytes adsorb onto charged surfaces in water, revealing that hydrophobic chains form pearl-necklace structures influenced by chain length and charge fraction.

Contribution

It provides in situ high energy X-ray reflectivity measurements of adsorbed polyelectrolyte layers, demonstrating the dependence of layer thickness on chain length and charge fraction for hydrophobic polyelectrolytes.

Findings

Layer thickness scales with chain length as N^0.

Layer thickness scales with effective charge fraction as f_{eff}^{-2/3}.

Hydrophobic polyelectrolytes adopt pearl-necklace conformations.

Abstract

A series of well-defined hydrophilic and hydrophobic polyelectrolytes of various chain lengths $N$ and effective charge fractions $f_{eff}$ have been adsorbed onto oppositely charged solid surfaces immersed in aqueous solutions. \emph{In situ} high energy X-ray reflectivity has provided the thickness $h$, the electron density and the roughness of the adsorbed layer in its aqueous environment. In the case of hydrophobic polyelectrolytes, we have found $h\propto N^0 f_{eff}^{-2/3}$, in agreement with a pearl-necklace conformation for the chains induced by a Rayleigh-like instability.